1. Field of the Invention
This invention relates to a spherulizing furnace for manufacturing vitreous beads comprising feed means for delivering particulate feedstock, a spherulizing zone in which the feedstock particles may be heated and converted to vitreous beads, and means for collecting the resulting beads. The invention includes a process of manufacturing vitreous beads in which feedstock is delivered to a spherulizing zone and passed along it so that the feedstock is heated and converted to vitreous beads whereafter the beads are collected. The invention extends to vitreous beads made by such a process.
2. Description of the Related Art
In classical spherulizing furnaces, particulate feedstock is fed to the base of a vertical cylindrical combustion chamber where it is surrounded by a burner flame in a spherulizing zone and entrained upwardly. The feedstock particles become spherulized by contact with the flame, and the resulting vitreous beads are carried out of the top of the combustion chamber in a stream of hot gas, and thence to cyclones for grading and collection. The feedstock particles are delivered to the combustion chamber in a stream of carrier gas, usually air, or a mixture of air and combustible gas.
As is well known, the way in which the feedstock is heated is of major importance to the economy of the process, and also to the quality and yield of the vitreous beads produced, particularly when those beads are to be cellular, for example monocellular. Rapid heating is beneficial for spherulization and/or vitrification of the feedstock, and this requires good thermal contact between the flame and the feedstock. In order to achieve a product of uniform quality it is important that the beads formed by the process should have been treated uniformly in the combustion chamber, and it is also important to reduce any tendency for the solid material to agglomerate. Thus the particles should be delivered in such a way that they are reasonably well separated both to reduce their tendency to agglomerate and so that they do not shield one another from the heating, and also the feedstock should be delivered in a uniform manner. For introducing the feedstock particles into a carrier gas stream for delivery to the spherulizing chamber, various proposals have been made with this end in view, but they have not been wholly satisfactory.
It is an object of this invention to provide a spherulizing furnace having improved feedstock delivery means.